I recommend writing down everything you want included. Ie. air con, appliances, hot water service, floor coverings etc. that way when you get quotes they are all apples for apples. Some builders leave out items and they will be an extra. It's always better to have your full cost up front.

Also start looking at your fixtures like taps, toilets etc because they can vary greatly between quotes and you may be getting something cheap and nasty.

Meet with the builder, ask if you will be able to have contact with the site supervisor or the project manager. Personal contact is an important thing when building your own home. Things will go wrong with a build but if you have good communication and rapport the issues can get sorted a lot easier.

If I think of more i'll add